Apparatus for hydrocarbon oil conversion



Aug. 19, l941. J. G. ALTHER 2,253,006

APPARATUS FOR HYDROCARBON OIL CONVERSION Original Filed April 17, 1929 &

J72 dzz for: Jsep)? flizker Patented Aug. 19, 1941 APPARATUS FORHYDROCARBON OIL CONVERSION Joseph G. Alther, Chicago, Ill., assignor toUniversal Oil Products Company, Chicago, 111., a corporation of DelawareApplication December 4, 1935, Serial No. 114,182,

which is a division of application Serial No. 355,704, April 17, 1929.Divided and this application February 15, 1938, Serial No. 190,634

4 Claims.

This is a division of my co-pending application Serial No. 114,182 filedDecember 4, 1936 which in turn is a division of SerialNo. 355,704 filedApril 17, 1929, which has matured into Patent 2,091,261.

This invention relates to improvements in apparatus for hydrocarbon oilconversion, and refers more particularly to improvements designed forthe eflicient cracking of hydrocarbon oils to convert and producetherefrom products having higher commercial value.

The utility of the invention as well as many objects and advantagesthereof will be brought out in the following description.

The principal object of the invention is to subject hydrocarbon oil tosuch conditions of temperature and pressure as to produce maximum yieldsof lighter gravity products suitable for use as motor fuel with aminimum coke and gas loss.

Another object is to carry out the operation in such manner as to causethe non-vaporous residue to accumulate in a low: pressure zone.

Another object is to provide in a cracking apparatus means whereby it ispossible to approach dry distillation. 7

Another object is to provide for lowering the reflux ratio by making itpossible to convert a greater proportion of the higher boiling pointhydrocarbons per pass throughthe stock. This is of particular importancein effecting the capacity and thermal efliciency of the process.

In one type of operation practised commercially on a large scale, theconditions o11 operation are so controlled as to mainly produce agasoline-like product suitable for use as motor fuel, which is thedesired product of conversion, and a substantially solid coke-likeresidue. Such operation is described as a non-residuum type ofoperation, the expression residuum in such instance meaning liquid Theoperation is carried out in a tube and drum type of apparatus whereinthe oil is heated in the tube and discharged into the drum whereseparation takes place between the lighter and heavier products ofconversion, both the tube and drum being maintained under substantiallysuperatmospheric pressure.

In a conventional non-residuum type of operationit is possible toapproach dry distillation,

accomplishing same in the drum, for the reason that there is aseparation in the drum to dryness, which is the coke-like, residue,practically all volatile matter having been distilled ofi. One of to theheavy material in the drum to be reduced to a coke solid. It is notbelieved that this could be done if it were not for the fact that thereis constantly supplied to the drum a large amount ofheat by the incomingoil to carry on this redueing or coking action.

As is well known, such type of operation proof a drum or still operatingunder little or no pressure. A flashing operation has advantages as wellas disadvantages, one of the advantages being a longtime onstream beforeshutting down. Some of the disadvantages are limited gasoline yield andlargeamount of liquid residue or fuel oil which may be unmarketable insome instances because of high viscosity. As a matter of fact the finalliquid residue or flashed residuum which is withdrawn from the flashingstill resembles a productwhich is uncracked. I do not mean to indicatethat this oil was not cracked but merely that it resembles an uncrackedoil. This may be due to polymerization, or it may be the direct resultof decreasing the time to which residue is normally subjected in anon-residuum type of operation. Or, the high Viscosity of the finalflashed residue may also be due to lack of heat while flashing.

It has been determined that, in a non-residuum type of operation, thereis practically a complete distillation, that is, all or substantiallyall of the volatile matter is removed from the drum through the vaporline and what remains in the chamber is substantially a solid. Theflashing operation is different'a relatively lower percentage of the oilleaving the pressure drum leaves that drum through the vapor line in theform of vapors. The bulk of the oil is withdrawn from the bottom of thepressure drum and flashed into the reduced pressure flashing stillwhere, due to the pressure reduction, full benefit of the heat containedin the oil is obtained to carry on the distillation or separation ofthis oil.

From the foregoing it will be apparent that from 100 to 1009 pounds,more or less. 'sion takes place in the drum from which substantially alloil, vapor. and gas may be withdrawn through a single outlet beingdirected into a large flash drum where flashing takes place ofoperation, the conditions being so controlled in the flashing still asto produce either a good residue suitable for asphalt making stock, or asubstantially solid coke, as local conditions may dictate.

From the foregoing it will be apparent that there is a pressuredistillation or separation in the pressure drum and a seconddistillation or separation in the reduced pressure flashing still.

The purpose of the present invention is to embody in an efficientapparatus the desirable features of the non-residuum and flashing typesof operation, the conditions being so controlled in the flashing stillas to produce either a good residue suitable for asphalt making StOCkl,or a substantially solid coke, as local conditions may dictate. V

Another purpose of the invention resides in the employment of means toincrease the decomposition of both the vapors and liquid from thepressure expansion drum under controlled conditions designed toaccomplish the best results. This feature not only has an effect inincreasing the yields of lighter hydrocarbons contained from theoperation but also in improving their quality, especially for use as amotor fuel, in that they will consist more largely of higher anti-knockcompounds.

It will be understood that the expansion drum may be operated at or nearthe same temperature as the coil outlet but may vary either above orbelow depending upon the nature of' the stock being treated and. theresults desired. temperature is maintained at or slightly'above that ofthe coil outlet, an advantage will accrue in that said drum may be ofmuch smaller size than if a material temperature drop is, allowed toprevail, as in the case where the chamber obtains no heat from externalsources. 7

The pressures on theexpansion chamber may 7 be substantially that of thecoil outlet or lower,

but in the preferable operation this pressure should be as high aspossible in order to increase the capacity of the unit and raise thethermal .efliciency of the process.

Briefly, the operation of the apparatus of the present invention is asfollows:

place, i. e., all the vapors from the flashing still are directed to adephlegmator where the sumciently converted fractions are separated fromthe insufiiciently converted fractions or heavy ends (reflux) by theincoming cold raw oil or other cooling medium, said reflux beingreturned I to the the cracking coil for retreatment.

If the The charging stock plus reflux will be pumped 7 through aconventional furnacehaving a large heating surface from which the heatedoil may be transferred to a drum. This drum is prefer ably heated byplacing-it in a heating zone to permit temperature control, or it may beunheated but lagged against excessive radiation losses. The oil in thecoil and the drum is maintained under superatmospheric pressure rangingExpanby reduction in pressure; or vapors may be withdrawn separatelyfrom the pressure drum, passing, to a dephlegmator, or preferablythrough' a vapor heating coil to provide further conversion and theninto a zone of lower pressure into which the residual oil from theexpansion drum may tion therein; or a combination of both methods may beemployed.

From this point on the usual operation takes- The main feature of theinvention is to have the oil which is undergoing treatment in the tubesand in the pressure drum at such temperature and pressure that, when theoil is released in the flashing still there will be sufficient latentheat to give practically an instantaneous dry distillation, that is,separation of all liquid in vapor form which leaves the flash still atthe top and the accumulation of substantially solid residue in thebottom.

If it is found in some instances that this coinplete separation or drydistillation is not accomplished, then resort can be had to the use of aheating medium to impart additional heat to the flashing still to drythe carbon by driving ofl all volatile matter.

From the foregoing it will be appreciated that one of the fundamentalsof the invention requires that coke or carbon formed in producing amaximum yield of gasoline is formed outside of the pressure zone.

From the foregoing it will also be seen that I I of the apparatus of theinvention.

Referring to the drawing and to the operation of the invention, the oilto be treated is directed through line I and branch 2, having valve 3into a heating coil 4, located in a conventional furnace 5. I

In heating coil l the oil is heated to a temperature within thecrackingrange under a suitable pressure. The amount of oil passedthrough the coil per unit time, and the size of the apparatus are socorrelated that under the temperatures and pressures used the degree ofcracldng ob tained in the heating'coil is preferably short of thatdegree of reaction at which formation of coke and sludge-like matteroccurs, or exceeds a predetermined desired degree.

Chamber It may take any desirable form and size in relation to thecapacity of theapparatus. It may be unheated and insulated against lossof heat by radiation; or, as shown in the drawing, it may be heated forthe purpose of main-,

. Proper control of the degree of heat furnished to chamber I0 may beobtained by regulation of suitable dampers shown 'at 15, spectivelylocated in flue l4 and and I3.

While, for the treatment a most oils, it may l1 and I8 reby-passes I2 bedesirable not to raise the temperature of the materials entering chamberII] to a temperature substantially higher than that prevailing at thedischarge of the heating coil 4, this is not to be takenas a limitation,since charging stocks, particularly the lighter ones, may be heated inchamber Ill to a temperature above that prevailing at the discharge ofcoil 4. On the other hand, particularly for the heavier charging stocksand depending upon the limitations imposed upon the amount of coke andsludge to be formed or contained in the products, it may be desirable tomaintain the materials in chamber l at a temperature lower than thatreached at the discharge of heating coil 4 to decrease the rate at whichthe reaction proceeds in chamber H]. To this end chamber In may beunheated or the oil may be cooled in a manner hereinafter described.

The vapors pass out of chamber l0 through line |9 having valve 20 todephlegmator 2|. As a feature of the invention I may subject all or partof the vapors removed from chamber ID to additional heating at elevatedtemperatures to effect a controlled degree of so-called vaporphasecracking whereby I am enabled to produce lighter valuable distillateshaving the characteristics of motor fuels or gasoline, possessing highanti-knock properties due to the presence of controlled proportions ofaromatic and unsaturated hydrocarbons formed by said vapor cracking.

For this purpose a vapor coil 22 may be positioned in furnace andlocated therein in such a manner that the combustion gases pass overcoil 22 before passing over coil 4. In this manner and because thecombustion gases passing over coil 22 are at a higher temperature thanwhen they pass over coil 4, a greater degree of radiant heat may beutilized in coil 22 than in coil 4. Coil 22 may be connected to vaporline l9. through branches 23 and 24, respectively, controlled by valves25 and 26. By proper regulation of valves 20, 25 and 26, any desiredamount of vapors separated in chamber l0 may be passed through the vaporheating coil 22.

Referring now to the dephlegmator 2|, the vapors remaining uncondensedtherein leave the upper part thereof through line 21, having valve 28,through condenser 29 and thence to receiver 30. Receiver 30 is providedwith the usual gas release line 3|, having valve 32, and distillaterelease 33, having valve 34. A portion of the distillate collected inreceiver 30 may be returned to the dephlegmator to facilitate closerfractionation. To this end line 35, pump 36 and valve 31 are provided.

The reflux condensate formed in dephlegmator 2| may be withdrawn fromthe bottom thereof through leg 38 and through line 39, in which may beinterposed a hot oil pump 49 andvalve 42, and through which said refluxcondensate may be directed to the main feed line I, whereby it may bereturned for retreatment to the heating tubes 4 with a supply of freshcharging stock.

Raw oil to be treated in the process may be drawn from suitable storagetanks (not shown) through line 43 and pump 44. From line 43 and bysuitable control of the valves shown, all or a portion of the raw oil tobe treated in the process maybe diverted through line 45, having valve46, then to line 41 which connects with the main feed line whereby allor a portion of the charging stock may be fed directly to the heatingtubes, mixing before entering therein with reflux condensate, directedthrough line 39. Or, all or a portion of the raw oil may be divertedfrom line 43 through branch 48, having valve 49, and then through line50 from which it may be directed to the dephlegmator, 2| to helpfractionate the vapors therein. Raw oil fed to dephlegmator 2| isthereby preheated and mixed with reflux condensate and the mixture maybe directed to the heating coil 4, through lines 38, 39 and l asheretofore described. If desired, the line may terminate in a closedcoil (not shown) connected to the feed lines 39 or 4! instead of mixingdirectly with the vapors.

I have discovered that when the degree of conversion obtained in thecracking zone, such as heating coil 4 and chamber I0, is so controlledthat the heavier liquid products separated therein do not contain morethan generally 5% and preferably less than 2%, of sludge-like orcokelike materials, as may be determined by so-called benzol centrifuge,said heavier liquid products comprise a substantial proportion offractions, which, when separated from such solids or sludge-likematerials under proper conditions, may be subjected advantageously toadditional conversion, with the formation of substantial additionalyields of motor fuel. This may be effected by regulating the conditionsin coil 4 and chamber H), or by subjecting the heavier liquid productsWithdrawn from chamber Hi to such additional treatment as willhereinafter be described, that a so-called dry distillation thereof isefiected, leaving in the zone of distillation a substantially solidresidue, the remaining fractions having been vaporized to produce amaterial which may be subjected advantageously to additional cracking.

The heavier liquid products are separated and withdrawn from chamber I0,preferably from the bottom thereof; or at various low levels as providedfor by a plurality of draw-oif lines and valves 50', through line 5|,having valves 52 and 53 interposed thereon, are directed to a flashchamber 54 to be subjected therein to flash distillation to any desireddegree.

By means of reduction of pressure obtained by proper control of valvesshown, a large portion of said unvaporized liquid products may bevaporized in chamber 54. Depending upon the conditions under which theoperation is carried out and upon the charging stock used, suchreduction in pressure may be suflicient to distill or vaporize saidheavier liquid products substantially to dryness by means of theself-contained heat. However, I have found that generally thisself-contained heat is not suflicient and in a majority of cases it isnecessary to give additional heat to the heavier liquid productswithdrawn from the reaction zone before subjecting them to flashdistillation in order to obtain during flash distillation a vaporizationsubstantially to dryness. According to one of the features of theinvention any desired proportion of, or all, the heavier liquid productswithdrawn from the reaction zone i9 may thus be directed. throughbranches 55, having valves 55 interposed thereon, through a heating coil58 located in furnace 5.

It may be desirable to regulate the heating of the heavier liquidproducts of reaction in such a manner that, while they receive thenecessary additional heat to cause substantially dry distillation byaccompanying or subsequent reduction of pressure, at the same time theadditional heat to which suchproducts are subjected does not causesubstantial additional cracking to take chamber H] in the shortestpossible time.

valves lit.

6!, having valve 52 and by-pass t3 controlled by point that rapid heattransfer takes place, so that the amount of heat required may betransmitted to theheavier liquid products of reaction in the shortestpossible time. In this manner I materially decrease the additionalcracking to which such products would be subjected, if they were heatedto the required temperature with a slower rate of heat transfer. Forthis purpose I have shown, in the drawing, the heating coil '58positioned near the hottest part of furnace 5, whereby, with the help ofintense radiant heat and high heating gas temperatures the non-vaporizedproducts withdrawn from chamber It may be raised rapidly to the requiredtemperature.

The sizes of heating coil 58 must be carefully proportioned relative tothe amount of materials to be fed therethrough and with the degree ofheat transfer therein. To assist in the regulation of the heat transferin heating coil l, vapor coil 22 and heavier liquid products coil 58respectively, which may be'more or less independent of eachother, I mayprovide furnace 5 with such means as are well known to regulate thetemperature and the amount of combustion gases therein. Such means are,for instance, flue gas recirculation, superheated steam injection andadditional burners properly located in furnace 5. Such additional meanshave not been shown on the attached drawing, as I believe theyare wellknown and would simply complicate the drawing.

By the proper control of the degree of reaction obtained in the zones 4and land by proper'control of valves 52 and 56 as well as by the controlof the heat transfer to coil 58, more or less independently of the heattransfer to the outer coils shown as heretofore explained, any desiredadditional amount of heat may be given to the heavier, liquid productswithdrawn from In this manner and coupled with proper control of thedegree of reduction of pressure to which said heavier liquid productsmay be subjected by means of either valves 52, 56 or 53, substantiallydry distillation of said heavier liquid products is effected in chamber53 without materially increasing the comparative amount of cokeformation in the process.

Or, chamber 54 may be provided with suitable heating means, such as coil59 controlled by It is provided with bottom draw-off valves 54, on whichmay be interposed pump 65, whereby liquid or semi-solid products may beremoved therefrom. Solid matters formed in the operation of the processand deposited in chamber 52 may be removed therefrom through top orbottom manholes in the usual manner.

One of the principal features of this invention is having the bulk ofthe carbon or coke deposition outside the zone of high pressure. Thispermits the use of much cheaper equipment as well as minimizing thedanger of explosion.

Vapors separated by flash distillation in chamber iii may be removedtherefrom through line 66 having valve 6?, whereby they may be passeddirectly to condensing and collecting means and in part or in totalremoved from the process or returned to the heating zone forretreatment. Or, as shown inthe drawing, they may be passed firstthrough a fractionating column 69, wherein they may be subjected tocontrolled condensation by introducing to dephlegmator 69 suitablecooling medium through line it, having valvell or raw oil to be chargedto the process maybe diverted from line 53 through line 12, having valvei3 and introduced to column 69.

Vapors uncondensed in column 69 may be removed therefrom through upperdraw-off line M, having valve 15, and passed to condenser '16, thenceto'receiver 11, having usual gas release valve 18 and distillate releasevalve 19. The fractions of the flash vapors condensed in column 69 maybe discharged from the bottom thereof through line 80, on which may beinterposed pump 8i. Thence, they may be diverted through branch 82having valve 83, which connects with line 50 whereby said fractions maybe returned to the process through dephlegmator 2 I. Or, the fractionscondensed in tower 69 may be passed through branch 84, having valve 85,connected with feed line 41, whereby said fractions may be returneddirectly to heating coil 4.

It will be apparent from the drawing that by suitable control of valves13, 49, 46, 85 and 83, any desired proportion of fresh raw oil or ofmaterials withdrawn from the bottom of tower 69, independently of'eachother, or together, may be directed to dephlegmator 2|- or to theheating part of the process.

It may be desirable to control the degrees of reaction respectively"taking place in heating coil i, chamber 50 and vapor coil 22, bycontrolling the temperature, characteristics and quantity of thematerial passing respectively through these zones. For instance, it maybe desirable to introduce into the oil transferred from the heating coil4 to chamber lil, liquid products or condensates from otherparts of theprocess. It may also be desirable to do the same thing for the vaporswithdrawn from chamber H). To this eifect a portion of the refluxcondensate. or combined feed passing through line 39 and being directedto the heating coil 4 may be diverted r from line 39 to branch Bl bysuitable control of valve 42 in line 39 and valve 86 in line 8'1. Inthis manner this material may be injected into line 8 combining thereinwith the products passing from heating coil 4 to chamber Ill. In thesame manner a portion of these materials maybe diverted from line 39through line 88 by suitable control of valve 42 and valve 39 in line 38,and through line 88 this material may be injected into line 90 whereinit combines with vapors passing from chamber Hi to the vapor crackingcoil 22.

In. addition it may be desirable to cool the vapors immediately afterthey have been subjected to vapor phase cracking in coil 22 and for thispurpose suitable lines and valves (not shown) may be provided wherebymaterial passing through line 41 or through line 39 may be diverted andinjected into line 2d through which the vapors leavethe coil 22. Insteadof inject ing' into the various parts of the system as heretoforedescribed, liquid products or condensate, it may be desirable. tointroduce thereto gases whether produced by the process or fromextraneous sources and which may have either a catalytic, hydrogenatingor oxidizing action.

While I have indicated in a diagrammatic manner, for the various partsof the apparatus a type of construction, it is to be understood thatother types of construction may be used for such parts, providing thatthe substituted parts permit of accomplishing the same function andobtain the same results as such parts of the construction showndiagrammatically on the attached drawing. For instance, a vapor phasecracking chamber suitably heated, may be substituted for the vaporheating coil 22. A so-called soaking coil, or digestion chamber, may besubstituted for the chamber l shown, but if such is used it ispreferable to connnect it with a separating chamber, which may beunheated, such soaking coil (or digestion chamber) and separatingchamber performing the functions of the chamber herein shown anddescribed. As another modification it may be desirable to interpose inline 24, connected with the discharge of the vapor coil 22 or itsequivalent, a separator whereby heavy products of polymerization formedby the vapor phase cracking effected in coil 22 or its equivalent, maybe separated from the vapors before passing the latter to dephlegmator2|.

The valves and pumps shown permit the operator to maintain suitablepressures on the various parts of the apparatus. The flash chamber 54and its connected parts such as dephlegmator 69, condenser 16 andreceiver H are preferably maintained at a pressure substantially lowerthan the pressure maintained in chamber I0. Dephlegmator 2| may bemaintained at any desired pressure equal to or lower than the pressuremaintained on vapor coil 22. The same pressure as that on dephlegmator2lor reduced differential pressures may be maintained on condenser 29and receiver 30.

The pressure maintained on the heating element 58 may be the same asthat maintained on chamber H1, or the same as that maintained on flashchamber 54 or an intermediate pressure. A proper control of the pressuremaintained on heating element 58 helps to control the heat transfer andthe velocity in said coil by proper regulation of vaporization therein;for instance, it may be advantageous to maintain element 58 at apressure lower than the pressure maintained in chamber In to permit acertain degree of' vaporization of the liquid products withdrawn fromchamber Hi to take place therein, the balance of the vaporization beingeffected in flash chamber 54 under further reduced pressure, asheretofore described.

Any suitable pressure may be maintained on vapor cracking coil 22 inrelation to the pressure maintained in chamber II].

If desired, vacuum may be maintained on the flash chamber 54 and itsassociated parts 69, and 11. This may be effected by proper use ofvacuum pumps (not shown), which would be connected to line 65 or to thedraw-offs from condenser 16 or receiver 11. It may be preferable to usevacuum on this part of the process when the conditions of operation aresuch that, should the pressure be reduced on flash chamber 54 down toatmospheric pressure, dry distillation of the heavier liquid productsdrawn off from chamber I0 could not be effected without such additionalheating in heating element 58 that objectionable reaction and excessiveformation of coke and sludge proceeds, even with the use of rapid heattransfer as contemplated by my process. The use of vacuum would thusreduce the additional amount of heat required to cause dry distillationof the heavier liquid products of reaction, and would thus obviate thedifficulty and disadvantages just mentioned.

In addition, the conversion may be effected through heating coil 4 orchamber 10 or its equivalent as heretofore described, under equalizedpressure, or the pressure maintained on chamber 10 may be lower thanthat maintained on heating 'coil 4 although still substantially aboveatmospheric pressure.

When vacuum is used, parts of the apparatus, such as vapor lines andcondensers, may be enlarged in proportion to their dimensions when usedunder pressure.

While I have described a particular arrangement of the various heatingzones of my process and a particular construction of the furnace 5 andheating chamber II, it is Within the scope of the invention to use otherrelative arrangements of these parts providing that such alternativearrangements permit the operator to carry outthe process in the mannerand for the purpose indicated with the results heretofore described.

For instance, each of the heating coils or v chambers 4, 22, 58 and I0,ifthe latter is to be heated, may be positioned in separate furnaces orheating chambers independently heated. In this alternative the furnacesor heating means in which vapor cracking coil 22 or its equivalent andelement 58 are located, may preferably be of such type as will permitthe use of rapid heat transfer such as caused by intense radiant heat,in the manner and for the purpose heretofore described in connectionwith the device shown in the drawing.

Or, the heated zones 4, I0, 22 and 58, or their equivalent, may bepositioned in separate heating chambers wherein, in addition to, orindependently of, the heat which may be produced by burners, theproducts of combustion which leave heating zones at relatively highertemperatures may be utilized in part or in total to help heat the partsmaintained at lower temperatures. For instance, the spent combustiongases leaving the furnace wherein heating coil 4 may be positioned, maybe utilized to help heat either one or more of the associated heatedzones ll}, 22 and 58. Or, the spent combustion gases leaving the furnaceWhere heating coil 4 is positioned maybe utilized to help heat thefurnace to which coil 58 may be positioned and the spent combustiongases leaving the furnace in which vapor coil 22 or its equivalent maybe positioned, may be utilized to help heat chamber l0. Any othercombination may be used to utilize best the heat of the process withoutdeparting from the scope of the invention so long as such alternativearrangement permits the operator to reach in the various heating zonesdescribed, the relative temperatures desired and to obtain therein therelative amount and rate of heat transfer which the process requires.

As an illustration ofthe temperatures which maybe maintained in anoperation carried out in accordance with the invention, the oil may beheated in heating coil 4 to a temperature of, say 920 F. to 960 F., saidoil entering chamber II] at a temperature near, but relatively lowerthan said temperature. In chamber 10 the oil may be maintained at atemperature of, say 850 F. to 900 F. In this illustration chamber Illmay not be heated, dampers H being closed and damper l6 being open. Thevapor leaving chamber I0 may be heated in vapor coil 22 to a temperatureof approximately 975 F. to 1100 F. and the heavier liquid productsremoved from chamber In may be passed through coil 58 and heated thereinto a temperature between 950 F. and 1000 F, and then directed to flashchamber 54. In this illustration a pressure of approxie mately 450pounds may be maintained on heating coil 4 and chamber in. The pressuremaintained on heating coil 58 may be approximately 250 pounds, and thispressure may be reduced on flash chamber 54 down to approximately 25pounds. The vapors leaving chamber l may be passed through vapor coil 22under a pressure of approximately 100 pounds, more or less.

While it will be apparent that the modifications referred to in theforegoing description refer mainly to the disposition of the heatingzone as well as to the arrangement of the conversion zone and partsdirectly connected therewith, it is to be understood that othermodifications may be made to the same or other parts of the apparatusused to carry out the invention without departing from the spirit of theprocess described herein.

While I have described in the apparatus shown in the drawing suchrelative arrangement of parts wherein heating element 58 is positionedin a hotter zone of the furnace than that in which vapor coil 22 isshown to be located, I may reverse the location of these two heatingelements.

Under these conditions and treating a Mid- Continent topped crude havinga gravity of approximately 28 B., a yield of about 60% of 437 F. endpoint gasoline may be produced, with the accompanying production ofapproximately 20% to 25% of so-called naphtha bottoms and gas oils, thebalance being solid residue and gas.

While I have shown and describeda single dephlegmator, it is to beunderstood that the invention may be used in connection with a crackingapparatus and method wherein two or more dephlegmators in series orparallel are used and particularly to such types of apparatus and methodwhere the vapors from the first dephlegmator are subjected to additionalfractionation through a secondary dephlegmator, which may be of anysuitable type.

As a means of facilitating the operation for the production of dryresidue, a portion of the noncondensable gas from receiver [1 may bereturned to vapor line leaving reaction chamber I0 by means of valve 92in line 93. This gas will pass through coil 22 together with the vaporsfrom the reaction chamber or be by-passed through valve 20 dependingupon the operation desired. In either event, by controlling valves 51 onflash chamber 54 the uncondensed gas and vapors may be introduced at anyone or more of several points therein. In the event the liquid level inchamber 54 is above any one of these points the hot gas and vapors willact as a partial pressure agent to facilitate vaporization and promotedistillation to dryness.

Two methods of operation are contemplated. In the first method, both thevaporous and unvaporized oil will be withdrawn through line 5| ,from thebottom of chamber Land passed to flash chamber 54 after reduction inpressure. The advantage of this procedure, especially with non-residuumoperations, will be that ,material partial pressure 'efiect will beexerted by the vapors, tending to increase the amount of vaporizationvin the flash chamber and decrease the amount of non-vaporous fractionstherein.

In the second method of operation, vaporswill be separated and withdrawnthrough vapor line 23, while the residual oil will be withdrawn from thebottom of the chamber through line 5|. Provision is made to permitbleeding off of a regulated quantity of vapors'from line H! into lineI00 by proper regulation of valve lfll. By controlling the point ofentry by means of valves 51, the vapors may enter flash chamber 54either above or below the liquid level maintained therein. If fulladvantage of partial pressure effect of these vapors is to be taken,they should enter in the lowest point in chamber 54 in order to increasevaporization and facilitate reduction of the percentage of unvaporizedoil.

It is to be understood that the preferred method .of operation is of thelow level type, wherein a minimum quantity of residual oil is maintainedin the pressure drum I2. That is, residual oil is withdrawn from chamberll] before it has had sufficient time to form more than 5% of sludge orcoke-like constituents.

I claim as my invention:

1. A cracking apparatus comprising a heating coil and a separatingchamber communicating therewith, a second chamber connected to andadapted to receive residual liquid from the separating chamber, afractionator, a final condenser and a receiver serially connected tosaid second chamber, means for heating vapors from the first-namedchamber and gases from said receiver, and means for discharging theheated vapors and gases into said second chamber.

2. A cracking apparatus comprising a heating coil and a separatingchamber communicating therewith, a second chamber connected to andadapted to receive residual liquid from the separating chamber, afractionator, a final condenser and a receiver serially connected tosaid second chamber, vapor communicating means between said chambers andincluding a second heating coil, and means for supplying gases from saidreceiver to said second coil.

3. The apparatus as defined in claim 1 further characterized in theprovision of a heater between the separating chamber and the secondchamber for heating said residual liquid in transit from the former tothe latter.

4. The apparatus as defined in claim 2 further characterized in theprovision of a heater between the separating chamber and the secondchamber for heating said residual liquid in transit from the former tothe latter. I

JOSEPH G. AL'I'HER.

